1. Field of the Invention
The present invention relates to a technique for preventing a power tool for performing an operation on a workpiece from malfunctioning.
2. Description of the Related Art
Japanese non-examined laid-open Patent Publication No. 2004-74298A discloses a known combustion driving power tool with a safety switch for preventing malfunctioning. According to the known tool, a control circuit executes injection of flammable gas into a combustion chamber when a push lever is pressed against the workpiece and a head switch is turned on. Thereafter, when a trigger switch is turned on, the control circuit actuates an ignition circuit to burn the flammable gas. Then, a driver blade 16 is moved by pressure generated by combustion of the flammable gas so that the nail is driven into the workpiece. The safety switch is provided between a battery and the control circuit and the control circuit is not energized when the safety switch is not on. Thus, the driving operation is blocked when the safety switch is off. On the other hand, the control circuit is defined by a microcomputer and may cause malfunctioning. For example, when the trigger switch is not on, a driving control signal may be outputted form the control circuit.